Recent advances in behavioral neuroscience have permitted investigation of the relations between developing areas of neocortex and emerging behavioral skills. The purpose of the current research is to examine in a non-invasive manner the relations between the maturation of central nervous system activity and performance on specific cognitive and affect eliciting tasks. The measure of central nervous system activity to be used is brain electrical activity recorded off the scalp (the electroencephalogram). 48 infants will be followed in a longitudinal study. The study will begin when infants are six months of age and end when infants are twelve months of age. Infants will be seen once a month. At each monthly assessment, 8 channels of EEG will be recorded while the infant is awake and sitting quietly. At each monthly assessment the infant will be presented with a set of tasks designed to tap specific cognitive behaviors and to elicit certain affective responses. The cognitive tasks will include the AE task with varying delay, object retrieval, and the Uzgiris-Hunt Scales of Object Permanence and Vocal and Gestural Imitation. The tasks designed to elicit affect include presentation of novel objects and masks and brief separation from mother. A cross-sectional sample will be collected to guard against practice effects and to examine discontinuities in development. Measures of power in different frequency bands and measures of coherence between different pairs of electrode sites will be computed from the EEG data. Utilizing current models of the EEG, relations between frequency components and coherence and infant task performance will be examined. These data will be among the first to investigate relations between changes in brain electrical activity and cognitive and affective task performance during the first year of life.